Production of doublet blanks for simulated diamonds

ABSTRACT

Improved process for the production of doublet blanks suitable for facetting into simulated diamonds by providing a first slab of a high dispersion, high refractive index material, such as strontium titanate or lithium niobate, of a thickness about equal to the thickness of the pavilion of a gem stone to be cut therefrom; providing a second slab of a material which is harder than the material of said first slab, and is substantially transparent with respect thereto such as white spinel or white sapphire; providing at least one of said first and second slabs of a surface area and dimensions equivalent to at least two finished facetted stones; rendering one major surface each of both of said slabs substantially flat surfaces; adhering such flat surfaces together; and cutting out individual gem sized doublets suitable for facetting from said adhered slabs.

Jones Aug. 28, 1973 1 PRODUCTION OF DOUBLET BLANKS FOR SIMULATED DIAMONDS [75] Inventor:

[73] Assignee: Chrom-Tronics, Inc., New York,-

[22] Filed: Jan. 17, 1972 [21] Appl. No.: 218,564

[56] References Cited UNITED STATES PATENTS 10/1965 Drown 125/30 12/1934 Schafer 156/101 X 11/1972 Zitzler et a1. 156/250 Harry S. Jones, Monmouth Beach,

Primary Examiner-Douglas J. Drummond Assistant Examiner-M. G. Wityshyn Attorney-Michael G. Gilman 5 7] ABSTRACT Improved process for the production of doublet blanks suitable for facetting into simulated diamonds by providing a first slab of a high dispersion, high refractive index material, such as strontium titanate or lithium niobate, of a thickness about equal to the thickness of the pavilion of a gem stone to be cut therefrom; providing a second slab of a material which is harder than the material of said first slab, and is substantially transparent with respect thereto such as white spinel or white sapphire; providing at least one of said first and second slabs of a surface area and dimensions equivalent to at least two finished facetted stones; rendering one major surface each of both of said slabs substantially flat surfaces; adhering such flat surfaces together; and cutting out individual gem sized doublets suitable for facetting from said adhered slabs.

11 Claims, No Drawings PRODUCTION OF DOUBLET BLANKS FOR SIMULATED DIAMONDS This invention relates to simulated diamonds. It more particularly refers to novel techniques for producing doublet simulated diamonds or blanks therefor.

In the simulated diamond trade, the raw or rough stone which is cut, facetted and polished into a sparkling gem is termed a blank. In the past such blanks have been made of spinel, sapphire, strontium titanate, titanium dioxide, zircon and various other materials. In every case the simulated diamond cut from such blank has had a combination of good and bad features. Some of these known materials have high refractivity and dispersion and are therefore quite lovely when cut into gem stones. However they are rather soft and are therefore easily scratched and chipped, even as a result of ordinary everyday wear and tear. Some of these known materials are quite hard, with hardness approaching that of diamond but, unfortunately, these hard materials lack the brilliance and fire usually associated with real diamonds due to their relatively low refractivity and dispersion. While each of these known materials has enjoyed some degree of commercial success, this has been far below expectations for the reasons given above.

In recent years work in this simulated diamond field has progressed toward a marriage of the appearance properties of the high dispersion, high refractivity materials with the strength and wear resistance properties of the hard materials. One of the marriage techniques has been to form a doublet stone utilizing as the pavilion, or lower portion, a highly refractive, high dispersion material, and using as the crown, or upper portion, a hard material, a material which is harder and therefore more scratch resistant than the pavilion material.

The doublet referred to above has been made commercially by cutting small pieces of pavilion material and of crown material to just larger than about the size desired for the finished gem-stone; then adhering the two small pieces together over a common substantially flat interface; and then cutting the thus-formed doublet blank into a finished gem stone. These doublet gemstones are quite attractive and in fact have substantially the same appearance as would a similarly cut stone of the pavilion material alone. Additionally, since the crown is of relatively hard material, such doublet gemface. According to this invention, the pavilion and crown material are adhered together in large slabs having a common interface sufficiently large to manufacture at least two, preferably many, gem-stones. Thereafter these large adhered slabs are cut into smaller sections and then facetted. It has been found that the total cost of doublet blanks (this is uncut stones), or for that matter of cut and polished gem-stones, is significantly reduced by practicing this invention, as compared to the prior art precedure.

Within the scope of this invention there are several techniques by which the precepts hereof can be carried out.

Therefore in one embodiment of this invention a rather large .slab of pavilion material, large enough to produce at least two, but preferably large enough to produce four or more blanks, is polished substantially flat on at least one major surface to make that surface smooth enough to juxtapose and bond to a crown mate rial. A suitable crown material of equivalent size has one of its major surfaces polished flat and is juxtaposed and bonded to the pavilion slab material through their common flat surfaces, which then become the interface of the adhered slabs. Appropriate sized doublet blanks are then cut out of this slab-sandwich. The doublet blanks can then be facetted and polished in the usual manner as gem stones.

In one alternative procedure the pavilion material slab can have two opposite major surfaces polished to a substantially parallel and flat condition and an equivalent sized slab of the crown material juxtaposed and bonded to each flat surface of the pavilion slab to form a crown-pavilion-crown sandwich. Doublet blanks may then be cut from such sandwich with minimum of wastage of material by using cuts at 45 to the flat surfaces. Blanks for emerald shaped stones may be cut more nearly perpendicular to the flat interface surfaces.

In another alternate procedure, a slab of crown material is polished substantially flat to prepare at least one major surface for bonding. Individual gem-stone sized, rough-cut pieces of the other material are polished substantially flat on one surface and bonded to such prepared surface whereupon the crown materials slab is out about each rough-cut-piece to yield individual blanks or sandwich blanks. To achieve most economical use of pavilion material the individual pieces of pastones are extremely resistant, when set in conventional jewelry settings, to ordinary wear and tear.

Unfortunately these doublet gem-stones have a significant commercial disadvantage, as compared to gem stones made wholly of the pavilion material, in that they are relatively expensive to produce.

It is therefore an object of this invention to provide a novel technique for producing doublet gem-stones and doublet blanks.

It is another object of this invention to provide a technique for producing doublet gem-stones and doublet blanks more economically than has been possible in the past.

In accord with and fulfilling these objects, one aspect of this invention resides in reversing some of the conventional processing steps whereby making it possible to achieve significant cost savings.

According to the prior art, the pavilion and crown,

portions are each separately rough cut into about the shape and size required for the finished gem-stone and are then adhered together through a common flat intervilion material may be appropriately spaced from each other on the crown slab to allow for material lost by the saw cut and for crown material needed when the girdle of the doublet is larger than the interface.

As a further adjunct and feature of this invention, individual facetted pieces of pavilion or crown material may be bonded to a slab of the other material. The individual pieces of material may be facetted to a desired final shape before adhering to the larger slab. This may be particularly desirable where machine facetting is available because after sawing into individual pieces it is then possible in one single operation to facet the surfaces of the crown or pavilion, as the case may be.

In practice, it is preferable to provide on the crown material at least a partial polish on the side thereof opposite to the interface side being bonded. This surface allows the progress of the cementing process to be observed in order to avoid bubbles, dirt or scratches. In blanks intended for jewels of all the same size, the remote surface may be more carefully polished parallel to the side to be bonded and held to a thickness appropriate for the jewel size selected. By this means the table facet will be completed in advance.

When desired, either the pre-facetted crown or pavilion portions may be hand or machine facetted, using material slabs pre-polished flat on one or both sides, as required.

The following examples are illustrative of this invention without being limiting thereon.

EXAMPLE I.

A slice of a strontium titanate boule having an average diameter of 19 mm is cut to a' thickness of 3.5 mm and polished substantially flat on its largest surface. Similarly, a 1.7 mm thick slab of white spinel, prefera bly of slightly larger area than the polished surface of the strontium titanate slab, is polished substantially flat on both sides, and with both sides substantially parallel. The polished surfaces of both parts are cemented together to form a bi-slab blank using any suitable optical cement such as the various lens cements sold by the Universal Shellac & Supply Company, Inc., Hicksville, New York. The second surface of the spinel slab is used to observe the cemented surface of the interface during the cementing process, so that bubbles, dirt or scratches may be eliminated if seen. The bi-slab thus produced may then be cut into four pie-shaped, substantially identical, individual blanks from which four 7 mm round stones of about l.5 carats may be facetted, after allowing about 1 mm for the width of each of 2-mutually-perpendicular saw cuts. Conventional sawing and polishing techniques may be used. Blanks for a variety of other jewel sizes and shapes may also be cut from such a large bi-slab, provided the thickness of the slab is appropriate. For example, blanks for two 9 mm round jewels, or two 16 X 8 mm marquise jewels may be cut from a 19 mm diameter bi-slab.

EXAMPLE 2.

Ina manner similar to Example 1, both sides of a 3 mm thick slab of strontium titanate are polished substantially flat and parallel. Two 1.6 mm thick slabs of white spinel are polished substantially flat andparallel and one slab is cemented to each polished side of the strontium titanate slab. Using an area of 12 mm X 12 mm at each cemented interface this tri-slab blank is then cut at 45 to the interface and also cut perpendicular to the plane of each 45 cut to yield four substantially identical, individual blanks from which four 6 mm round stones, each about one carat, may be faceted.

EXAMPLE 3.

Using spinel slabs of appropriate thickness similar to those described in Example 1, and polished substantially parallel and flat on both sides, these parts may be faceted as crown portions in large quantities by ma chine means, or by hand. One flat surface will serve as the table while the other surface is used as an interface surface. Therefore, only the crown facets need be cut. Strontium titanate pieces of appropriate thickness having one surface polished and having substantially the same area as the interface of the spinel crown portions are then cemented to these crown portions over their common interface. The pavilion portions of each of these partially faceted blanks may then be faceted to yield a complete doublet jewel. When desired, the girdle may be made larger than the interface when the pavilion is faceted. This may be accomplished by making the prepolished girdle wider'than its final width and by allowing the strontium titanate pavilion facets to extend over upon the spinel portion of the jewel.

EXAMPLE 4.

EXAMPLE 5.

Pre-faceted crown and pre-faceted pavilion portions, as described in the foregoing Example, may be cemented together to form complete doublets.

EXAMPLE 6.

Using a large slab of spinel which has been polished substantially flat and parallel on two opposite sides,several smaller pieces of strontium titanate polished flat on one side and shaped in a manner for use as a doublet pavilion blank may be cemented to one face of the spinel slab. ,These strontium titanate parts may be spaced inamount sufficient to allow for the small chips which sometimes result when the spinel plate is subsequently sawed to form several individual blanks. This spacing can also include sufficient spinel to allow the girdle to be made larger than the interface when desired.

EXAMPLE 7.

Using pre-faceted pavilion parts having a flat surface as described in Example 4, these parts may be substituted for the un-faceted strontium titanate parts used in Example 6. These pavilion parts may then be cemented to a large slab of spinel, as described in Example 6, with appropriate spacing. After sawing into separate blanks, as in Example 6, the individual blanks may then be faceted with crown facets and polished at the girdle with the interface beldw, at the bottom of, or inside the girdle.

' EXAMPLE 8.

In a manner similar to that described in Example 6, small slabs of spinel may be cemented to a large slab of strontium titanate and then cut into individual blanks by cutting between the spinel slabs.

EXAMPLE 9.

In a manner to that described in Example 7, prefaceted crown parts may be cemented to a large slab of strontium titanate leaving an appropriate space between each crown part. After cutting the strontium titanate slab into individual partial blanks, the pavilion parts may be faceted on each blank.

In one particular embodiment of this invention, there is the possibility that the pavilion material and the crown material have such different temperature coefficients of expansion that a potential problem is created. This problem involves the possibility that the adhered crown and pavilion will separate at their bonded interface during consumer wearing because of a sudden marked temperature change, e.g. immersing the gemstone in cold water while swimming or exposing it to hot summer sun. This problem is particularly troublesome with lithium niobate pavilion gem-stones.

A related problem with this same type of doublet lies in the fact that sometimes instead of the doublet separating at the bonded interface, the relative temperature responsive expansions cause cracking of either the pavilion or the crown material, usually the pavilion.

It has now been discovered, and itis a further aspect of this invention, that the difficulties encountered due to widely differing thermal expansion in the pavilion and crown can be overcome entirely or at least to a great extent by initially adhering the pavilion and the crown together at relatively low temperatures, e.g. about 60 to 20C, preferably about to 10C. In this aspect of this invention it is most desirable to utilize an optical cement, such as an epoxy based cement for example, which is hardened by the action of a nonheat producing means, such as ultra violet radiation for example. Where possible the cement should have a moderately short hardening or curing time. eg about 10 seconds to 60 minutes, preferably about 30 seconds to 6 minutes.

Suitable cements are available commercially under the name of UV-7l from Summer Laboratories of Ftwashington, Penna. Such suitable cements are believed to be based upon polyesters.

Other suitable cements are those which maintain a high degree of viscosity but are not solid in a set condition. This state can be accomplished according to techniques well-known in the art by including a compatible plasticizer with a high melting thermo-plastic cement.

What is claimed is:

1. In the process of producing a gem-stone blank for facetting from a pavilion material adhered to a crown material by the steps of flattening surfaces of said crown and pavilion materials, juxtaposing such flattened surfaces and adhering such surfaces together; the improvement which comprises providing at least one of said crown or pavilion materials as a first slab of a size large enough to yield at least two gem stone blanks therefrom; flattening at least one major surface of said first slab; providing the other of said crown or pavilion material in a total size corresponding to at least the size of said first slab; flattening a major surface of the other of said crown or pavilion material; adhering said flattened surfaces together to make a doublet slab sandwich comprising pavilion material and crown material of plan size sufficiently large to yield at least two gemstones therefrom; and cutting said sandwich into single gem stone sized doublet blanks.

2. The improved process claimed in claim 1 including flattening two opposite, substantially parallel major surfaces of said first slab; adhering the other of said pavilion or crown material to both of said flattened major surfaces to form a triplet slab; and then cutting doublet blanks from said triplet slab.

3. The improved process claimed in claim 1 wherein both of said pavilion and crown materials are in slab form of substantially the same overall plan size.

4. The improved process claimed in claim 1 including adhering said pavilion or crown material adhered to said first slab in the form of individual gem-stone sized pieces and including cutting said slab about said individual sized pieces.

5. The improved process claimed in claim 4 wherein said individual sized pieces are facetted prior to adhering such to said first slab.

6. The improved process as claimed in claim 1 wherein said pavilion material is a member selected from the group consisting of strontium titanate and lithium niobate and wherein said crown material is harder than said pavilion material and is a member selected from the group consisting of white spine], zircon, white sapphire titanium dioxide, diamond and yttrium aluminum garnet.

7. The improved process claimed in claim 1 wherein said adhering is carried out at about 60 to 20C.

8. The improved process claimed in claim 1 wherein said adhering is carried out at about 10 to 10C.

9. The improved process claimed in claim 7 wherein said adhering is by means of an optical cement which is hardened by the action of ultraviolet light.

10. The improved process claimed in claim 9 wherein said optical cement is epoxy based.

11. The improved process in claim 9, wherein said optical cement is based upon polyesters. 

2. The improved process claimed in claim 1 including flattening two opposite, substantially parallel major surfaces of said first slab; adhering the other of said pavilion or crown material to both of said flattened major surfaces to form a triplet slab; and then cutting doublet blanks from said triplet slab.
 3. The improved process claimed in claim 1 wherein both of said pavilion and crown materials are in slab form of substantially the same overall plan size.
 4. The improved process claimed in claim 1 including adhering said pavilion or crown material adhered to said first slab in the form of individual gem-stone sized pieces and including cutting said slab about said individual sized pieces.
 5. The improved process claimed in claim 4 wherein said individual sized pieces are facetted prior to adhering such to said first slab.
 6. The improved process as claimed in claim 1 wherein said pavilion material is a member selected from the group consisting of strontium titanate and lithium niobate and wherein said crown material is harder than said pavilion material and is a member selected from the group consisting of white spinel, zircon, white sapphire titanium dioxide, diamond and yttrium aluminum garnet.
 7. The improved process claimed in claim 1 wherein said adhering is carried out at about - 60 to + 20*C.
 8. The improved process claimed in claim 1 wherein said adhering is carried out at about - 10 to + 10*C.
 9. The improved process claimed in claim 7 wherein said adhering is by means of an optical cement which is hardened by the action of ultraviolet light.
 10. The improved process claimed in claim 9 wherein said optical cement is epoxy based.
 11. The improved process in claim 9, wherein said optical cement is based upon polyesters. 